Abstract

Heavy metal-ion pollution in water is a serious problem for the environment, and membrane filtration technologies such as nanofiltration (NF) have become viable treatment alternatives. However, it is necessary to understand the performance of NF as a function of effluent composition and membrane surface charge properties. This work evaluated first the impact of metal ions on the zeta potential using streaming potential measurements for a commercial NF membrane (NF270). Then, NF rejection of Ca2+, Cu2+, and Al3+ in sulphate and chloride solutions was analyzed based on zeta potential results. Reductions, neutralizations, and inversions of the surface charge of the membrane were observed through streaming zeta potential analysis. Our results also revealed significant differences of the zeta potential between divalent ions and aluminum under all experimental conditions studied. Based on the zeta potential measurements, it was possible to explain the rejects observed for the different metallic ions, through an analysis of steric and electric exclusion effects. Adsorption of ions caused also changes of membrane properties that were analyzed by ATR-FTIR, AFM and contact angles.